Community composition and floristic relationships in Montane wetlands in the North Cascades, Washington
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Montane wetlands in the North Cascades, Washington, USA were dominated by small red peat moss (Sphagnum capillifolium), white marshmarigold (Caltha biflora), and many spiked cottongrass (Eriophorum polystachion), the species with highest cover and frequency. Overall, 139 species were recorded in the 24 wetlands studied. Of the common species, nine were distributed independently of margin vs. central expanse locations, eight were more prominent in the margin habitat, and six were more prominent in the central expanse. Species diversity was described by species richness, and by Shannon-Wiener and Simpson's indices. These data were interpreted according to three wetland sizes (<0.5 ha; 0.5-1.5 ha; >1.5 ha) and margin vs. central expanse location. Species richness was significantly correlated with wetland size and was significantly greater in the larger wetlands. The Shannon-Wiener index was significantly correlated with wetland size and was significantly greater in wetland margins vs. central expanse. Simpson's index was unrelated to size or location in the wetland. Habitat heterogeneity in the wetlands was increased by buried logs, where conifer saplings were concentrated, even in the central expanse. North Cascades wetlands were distributed along gradients of elevation, annual precipitation, and degree of water movement. Lower elevation wetlands were characterized by higher annual precipitation and still water, whereas higher elevation wetlands were characterized by lower annual precipitation and moving water.